In recent years, catheter-using medical treatment of a vascular lesion is actively carried out because this medical treatment gives patients very low surgical invasions. There are proposals of catheters which can be inserted into a vascular system having a narrow and complicated pattern with a quick and reliable selectivity. Such catheters are proposed as disclosed in the following patent documents: Japanese Patent Application Laid-Open Publication No. 2001-218851 (patent document 1), Japanese Patent Application Laid-Open Publication No. 2006-51081 (patent document 2), Japanese Patent Application Laid-Open Publication No. 2006-158788 (patent document 3), and Japanese Patent Application Laid-Open Publication No. 2013-208150 (patent document 4).